Historically, magnetic recording media evolved from metal tapes to magnetic oxide particles held in an organic binder and carried by a polymer tape substrate. Particulate recording tape continues to be the dominant tape medium, with countless refinements introduced over the last several decades. However, a need for rapid access to stored data has developed with the growth of the computer industry. The sequential access of information stored on tape is too slow for many applications. Plated metal films on spinning drums were used for a time. The use of rotating rigid disks replaced drum storage since disks could be more easily coated and could be stacked and recorded on two sides, thus increasing the volume storage capacity compared with drums. Presently, particulate media dominate the disk as well as the tape industry. With the appearance of mini- and microcomputers, a third form of magnetic storage grew to major proportions, namely the flexible (floppy) disk. This technology is also dominated by particulate media.
The most commonly used magnetic media are particles of gamma ferric oxide. Other particles that are being used for more advanced applications include cobalt-modified gamma ferric oxide, chromium dioxide, and metal particles. In addition, barium ferrite has recently received increased interest in connection with its use in recording media for perpendicular recording. For example, next-generation camera-type or improved quality home video, digitally encoded audio, and professional video recording systems are expected to go to wavelengths as short as 0.5 micrometers. This requires the high remanence and coercivity values found with metal particle tapes. Barium ferrite platlettes, oriented for perpendicular recording, lend themselves to an extremely flat frequency response which may result in similar output levels as those of metal particle tapes at the target wavelengths below 0.5 micrometers. See C. Denis Mee et al., Magnetic Recording, Vol. 1: Technology, (1987).
There is presently a need for a system having the ability to discern the difference between various types of magnetic recording media, including ferric oxide, barium ferrite, and metal particle recording media. Such a system would allow a manufacturer to "mistake proof" assembly and test stations that process multiple media types. Other applications, e.g., in a tape playback apparatus, can also be envisioned.